This invention relates to a process for the production of a gas rich in methane from a feed gas of hydrogen and carbon oxides, wherein the feed gas, after its preliminary purification is warmed, then subjected to a multistage catalytic methanization, and thereupon is subjected to a CO.sub.2 separation.
It is old to methanize coal gasification gas consisting essentially of CO.sub.2, CO, CH.sub.4, and H.sub.2, as well as impurities, especially sulfur compounds, with the use of a suitable catalyst. After a final CO.sub.2 separation, the thus-obtained methane-rich product can be further utilized as a gas which can be substituted for natural gas (SNG). The details of such systems herein are described in the literature.
One difficulty of such a methanization process is caused by the presence of the sulfur compounds, which can lead to poisoning of the catalysts employed. To solve this problem, a preliminary step (prior to the methanization of the coal gasification gas) has been proposed to separate the sulfur compounds contained therein by means of suitable adsorbents, such as activated carbon or ZnO. Since the adsorbability of such adsorbents is, however, limited, and rather large amounts of sulfur compounds are contained in the coal gasification gas, a continuous operation is possible only with the use of several interchangeable adsorbers. This type of operation is, however, disadvantageously expensive.